Devices and methods for removing occlusions in vessels

ABSTRACT

Occlusion-removing devices that include an inflatable balloon for arresting blood flow and a occlusion-shearing element are provided. Also provided are methods of making and using these devices.

FIELD OF THE INVENTION

[0001] This invention relates to devices and methods for removing anocclusion from a vessel.

BACKGROUND

[0002] This surgical device is designed to remove occlusions found inthe human vasculature and thereby increase blood flow to and around theoccluded site.

[0003] Emboli occasionally form around the valves of the heart and thenare dislodged and follow the blood flow into the distal regions of thebody. They are particularly dangerous if the emboli is transmitted tothe brain where it results in an embolic stroke. As will be discussedbelow, many such occlusions occur in the middle cerebral artery (MCA),although such is not the only site where emboli come to rest. When bloodflow is inhibited or cut off completely from a portion of the brain, thebrain's oxygen supply is limited causing severe problems.

[0004] Such vaso-occlusions occur in a wide variety of sites within thebody. The lodging of thrombus in various sites is complicated by thepresence of atherosclerosis. This disease causes the vessels to becometortuous and narrowed. These anomalies are often considered to be theresult of the growth of atherosclerotic plaque. Clots occurring in thesediseased vessels are difficult to remove using known catheters.

[0005] The use of inflatable balloons to remove emboli has beenpracticed for many years. The “Fogarty catheter” has been used,typically in the periphery, to remove clots from arteries found in legsand in arms. These well known devices have been described in some detailin U.S. Pat. No. 3,435,826, to Fogarty. Other balloon-type devices aredescribed, for example, in U.S. Pat. Nos. 4,403,612; 3,367,101;5,078,722; 5,836,957; and 6,152,909.

[0006] Another approach for removing embolisms involves the use of anabrading device carried at the distal end of a flexible drive shaft.Examples of such devices are described, for example, in U.S. Pat. Nos.4,990,134 (Auth) and 5,314,438 (Shturman) which describe the use ofabrasive material such as diamond grit (diamond particles or dust) toremove hardened, calcified atherosclerotic plaques. Emboli fragmentingdevices have also been described, for example, in U.S. Pat. No.5,423,838. Other patents describe the use of cutting blades, typicallyextendable from a housing assembly for removing the occlusion byfragmentation. See, for example, U.S. Pat. Nos. 4,030,503; 4,890,611;5,411,509; 5,490,859; 6,001,112; 5,423,838; and 4,923,462. These devicestypically contain a catheter shaft, a drive shaft for spinning thematerial movement element within the blood vessel, and a collectionportion placed on the material removal element for collecting anyocclusion material removed by the expandable material removal element.The drive shaft may be operated by a motor connected to the drive shaftproximate to the proximal end of the drive shaft.

[0007] Despite the advances made using these devices, removal of emboliusing either balloon catheters or mechanical fragmenting devices is rifewith potential problems. When attempting to remove a clot using aballoon catheter, the resistance to such removal often causes theballoon portion of the catheter to evert over the tip of the catheter.Should the user need to partially deflate the balloon during such adeflation, the distal tip of the balloon may become distended andangulate. Another difficulty with balloon catheters is the possibilityof damage to the intima of arteries. Inflation pressures can createforces significant enough to share such a vessel lining or dislodgeplaque lodged on such a wall. In the worst case, the balloon may ruptureleaving balloon portions in the bloodstream. Movement of a balloon candisplace the clot through more proximal branches into other largevessels such as the internal carotid artery (ICA) and then into othervessels. Furthermore, if the occlusion is a blood clot or soft tissuethrombus, such as those that may occur in the peripheral vasculature,for instance, the soft tissues of the thrombus may sufficiently resistthe molding action of the dilating member (i.e. may be too elastic) toprevent conventional angioplasty from permanently restoring vascularblood flow. In addition, even if the occlusion is successfully molded,thereby revascularizing the vessel and restoring blood flowtherethrough, there is a chance that the occlusion may recur because theoccluding material is not removed from the vascular lumen, therebynecessitating repeated or alternative treatments.

[0008] Mechanical fragmenting devices can also cause serious problemsduring clot removal. For example, because embolisms are oftenasymmetrical or are similar in mechanical properties to the surroundingtissue, many of these devices can damage healthy tissue while removingthe clot. Furthermore, many fragmenting devices are not suited toremoving both hard and soft occlusions. Additionally, the fragmentsgenerated by mechanical fragmentation cannot always be efficientlyremoved and can cause problems if they are carried by the blood toremote locations.

[0009] Thus, notwithstanding the foregoing and other efforts to design aembolic removal devices, there remains a need for such a device whichcan efficiently remove all sorts of emboli while providing minimal riskto the surrounding vessel wall. None of the currently available devicesapproximates the design of the device described below.

SUMMARY OF THE INVENTION

[0010] In one aspect, the invention includes a device for removingocclusions from a vessel, comprising (a) a housing element having adistal end, a proximal end and a longitudinal axis, wherein one or morelumens are disposed along the longitudinal axis; (b) an embolismcollector element (e.g., a vacuum aspirator); (c) a cutting elementattached to the distal end of the drive shaft; and (c) an inflatableballoon. In certain embodiments, the device further includes one or moreof the following components: a fluid channel, a casing (e.g., acage-like structure) disposed around the cutting element; a drive shaftdisposed along the longitudinal axis of the housing and/or a powersource (e.g., a micro electro mechanical system (MEMS) motor). In any ofthese devices, the cutting element may be smooth, roughened and/or mayhave perforations therein. Similarly, in any of these devices thehousing and/or casing that contacts the cutting element is alsosurface-modified (e.g., is roughened, perforated, includes braids and/orribbons, etc.). In embodiments comprising a casing around the cuttingelement, the casing may extend from the distal end of the housing. Inany of the devices described herein, the inflatable balloon is capableof (a) centering the cutting element; (b) at least partially arrestingblood flow around the occlusion; or (c) both centering and arrestingblood flow.

[0011] In another aspect, methods of removing an occlusion in a vesselare provided. The methods comprise accessing a selected site with any ofthe devices described herein; inflating the balloon to the desireddimensions; shearing at least a portion of the embolism with the cuttingelement; and removing the sheared fragments of the embolism with thecollection element. In certain embodiments, the shearing comprisesdrawing a portion of the embolism into the housing and manipulating thecutting element to shear the embolism against the interior wall of thehousing and/or against the casing, when the casing is present.

[0012] These and other embodiments of the subject invention will readilyoccur to those of skill in the art in light of the disclosure herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 depicts one embodiments of a clot removal device asdescribed herein.

[0014]FIGS. 2A and 2B depict variations of the shape and surfacemodifications of cutting elements useful in the present invention andalso depict cutting elements which include a fluid channel disposedtherein.

[0015]FIGS. 3 and 3B depict other embodiments of a cutting burr, fluidchannel and protective casing (e.g., cage) disposed around the cuttingelement.

DESCRIPTION OF THE INVENTION

[0016] Devices and methods for the removal of emboli are described.Methods of using these devices also form an aspect of this invention.Currently, mechanical clot removal devices often result in the pieces ofthe clot being washed away. The present invention solves this and otherproblems by providing a means to stop blood flow in the vessel that isoccluded until the clot is captured, broken up and/or evacuated. Thedevice and methods described herein are particularly effective for theend stages of blood clot removal where the clot has created a largechannel to allow blood flow to break up and carry downstream fragmentsof the clot.

[0017] Advantages of the present invention include, but are not limitedto, (i) minimizing the potential that fragments of an embolism can becarried to remote locations by blood flow; (ii) providing the operatorwith the ability to control blood flow around the device; (iii)minimizing the likelihood of vessel perforation; and (iv) providing adevice suitable for a wide variety of occlusions.

[0018] All publications, patents and patent applications cited herein,whether supra or infra, are hereby incorporated by reference in theirentirety.

[0019] It must be noted that, as used in this specification and theappended claims, the singular forms “a”, “an”, and “the” include pluralreferents unless the content clearly dictates otherwise. Thus, forexample, reference to “a cutting element” includes a mixture of two ormore such elements and the like.

[0020] This device is a surgical implement which is designed to at leastpartially retrieve emboli situated in human vasculature. It is intendedto be used rapidly as a flow restoration device. Even in those instanceswhere the embolism is not or cannot be completely removed, thisinventive device is useful in removing a portion of the clot and therebypermitting restoration of partial blood flow. It is suitably flexible tobe placed in the distal tortuous vasculature of the brain and hence isuseful in treating blocking emboli found there. Accordingly, this devicecan used as a partial treatment for embolic stroke. As used herein, theterms “embolus,” “clot” and “occlusion” are used interchangeably torefer to any blockage (partial or full) of a vessel by any material(e.g., blood, lymph, plaques, etc.)

[0021] Thus, in certain aspects, the inventive device combines a cuttingelement, an inflatable balloon and other elements such that occlusionscan be removed. The device disclosed herein is for the recanalization ofoccluded vascular lumen (e.g., the middle cerebral artery (MCA) lumen),via the steps of accessing the site of the occlusion; expanding aninflatable balloon which is capable of partially or fully arrestingblood flow and is also capable of centering the device (particularly thecutting element); mechanically fragmenting at least a portion of theocclusion within the housing or within a protective casing covering thecutting element; and collecting the fragments through the device via acollection element such as a vacuum aspirator.

[0022]FIG. 1 depicts selected portions of one variation of the device(10). The assembly typically includes, within a housing (11), forexample a catheter body; a collection element (12), for example a vacuumaspirator for removing fragments of the embolus; and a drive shaft (13)operably linked to a cutting element (14) for fragmenting the clot. Thehousing (11) may include a channel to accommodate a guide wire or mayhave a fixed wire. Additionally, the housing may be attached to a distalcone to facilitate the delivery of the device over a guide wire.

[0023] As shown in FIG. 2, the cutting element can include a fluidchannel (20) for introducing and/or removal of fluids. The cuttingelement can also include multiple channels to incorporate fluid jets forintroducing fluids. The cutting element (14) can be external to theassembly housing or can be extendable from the housing. Furthermore, theassembly also includes an inflatable balloon (15) which serves to arrestthe flow of blood so that the fragmented pieces of clot are not washedaway by the flow of blood. Additionally, the balloon (15) also serves tocenter the assembly, thereby keeping the cutting element away from thewalls of the vessel.

[0024] The housing (11), for example a catheter body, may includemultiple lumens and/or multiple tubular members positioned within eachother. Methods of making and using multi-lumen catheter bodies are wellknown to those of skill in the art. Any of the lumens or tubular membersof the housing can further comprise a removable core or guide wire.Further, portions of the interior surface of one or more the lumens ofthe housing (11) may be braided (16) or otherwise modified on the innersurface to help shear the embolic material against the cutting element(14). The placement of a braid or other surface modifications can varyalong the length of the assembly, but is desirably at least from thedistal end of embolism collector element to the proximal end of thecutting element. Braids can be made, for example, of a superelasticalloy, stainless steel, radioopaque materials such as platinum, and evenorganic and inorganic fibers or ribbons such as KEVLAR and carbon fiberor combinations of the foregoing. A desirable variant is thesubstitution of one or more ribbons of the braid (or the addition of oneor more ribbons) with a radio-opaque material such as platinum. Thisobviously permits the user to visualize the position of the embolismcollector element during the clot removal procedure. Furthermore,surface modifications (such as by roughening the inner surface of thehousing) can also enhance shearing. Such surface modifications may bedone instead of, or in addition to, other modifications such asbraiding.

[0025] The housing may further include slots and/or openings dimensionedso that at least a portion of the occlusion can be drawn into thehousing through these openings. One or more lumens of the housing aredesirably, but not necessarily, made of lubricious material such aspolytetrafluoroethylene. Other materials such as polyurethane,polypropylene, polyurethane, polyurethane or polyethyline ofpolyvinilchloride, and materials widely known and used in this industrycan also be used. In certain instances, it may be desirable to etch theouter surface of tubing using known etching techniques to provide asurface suitable for joining for the other layers. Further it is oftendesirable to use a biocompatible epoxy such as TRA-CON TRA-BOND FDA-2(Tra-Con, Inc.—Medford, Mass.) as the material which provides adherencebetween the lumens of the housing.

[0026] The devices described herein also include an inflatable balloon,which serves, for example, to arrest the flow of blood and,additionally, to center the cutting element to avoid perforation of thevessel walls. Any suitable inflatable balloon can be used inconstruction and use of the devices described herein. Preferably, theballoon restricting the blood flow is very short, thereby allowing it tobe positioned on curves without straightening the vessel or blockingside branches. As will be apparent to those of skill in the art, theballoon can be manipulated by the operator to restrict blood flow invirtually any amount.

[0027] Exemplary cutting elements are shown in FIGS. 2-3. Although notshown in all FIGS, the associated elements such as balloon, optionaldrive shaft, vacuum channel and the like are all similar in constructionto those described above. The cutting element is capable of moving inany direction, including rotating (spinning), longitudinal movement andlateral movement. It will also be apparent that these movements can beimparted at the concurrently or at different times. Lateral andlongitudinal movement allow, for example, shearing of the occlusionagainst the wall of the housing and/or casing, described below.Preferably, the collection element draws at least part of the embolusinto the housing (or casing) where the cutting element can be agitatedby the operator such that the clot is sheared by the cutting element andadjacent walls of the housing. Thus, to minimize the likelihood ofvessel perforation, the cutting element is preferably only slightlyextendable from the housing. In other words, the cutting element worksin conjunction with the other elements of the device. The collectionelement is able to draw at least a portion of the clot into the housing,where the cutting element can then be rotated or otherwise manipulatedto shear the clot. The fragments are then evacuated by the collectionelement.

[0028]FIGS. 2A and 2B show variations in which the surface (22) of thecutting element is roughened by adding bumps or otherwise modifying thesurface. The shape of the metallic burr on the cutting element (24) isalso desirably formed such to provide added suction and added vacuum.Any design can be used, shown in FIG. 2A is a cylindrical shape burr,while FIG. 2B depicts a mushroom-shaped burr. Additionally, the cuttingelement preferably includes perforations (27) through which the clot orfragments thereof can pass through.

[0029] Also shown in FIGS. 2A and 2B is fluid channel (20). The channelcan be used for distal perfusion, for example with saline (e.g., oxygenenhanced saline). The channel can also be used to introduce any numberof pharmaceutically active fluids into the subject including, but notlimited to, neuro-protective and/or thrombolytic drugs.

[0030]FIGS. 3A and 3B show variations in which the cutting element (14)is placed within a protective casing (30), for example a cage-likestructure. As will be apparent the casing is desirably permeable tofluid and/or solid materials of varying dimensions. In embodiments inwhich the cutting element is within a casing, the cutting element mayextend farther from the distal end of the device as perforation of thevessel walls is minimized by the casing. The encased cutting element ispreferably still surface roughened such that fragmentation of the clotcan be achieved by manipulating the cutter element against the casing.

[0031] Like the housing, the casing may further include slots and/oropenings dimensioned so that at least a portion of the occlusion can bedrawn into the casing and preferably contact the cutting element throughthese openings. It may be desirable to etch or otherwise roughen theinner and/or outer surface of the casing to facilitate shearing of theocclusion, for example, as described above.

[0032] The casing is preferably made of a super-elastic alloy ribbon.Some stainless steels are suitable but the ready availability ofnickel-titanium alloys in a wide variety of shapes and sizes makes thischoice an easy one. In particular, we have found that ribbons as thin as0.75 mils in thickness and 2 mils in width are suitable for this device.Thicker and wider ribbons are also suitable in some instances as thesituation requires. Preferred ribbons for the embolism collector elementare between 0.75 and 1.5 mils in thickness and 3 and 7 mills in width.Most preferred are 0.08 mils and 4 mils respectively. Then use ofsuper-elastic alloys such as nitinol in surgical devices has beenpreviously described (see, e.g., U.S. Pat. No. 6,066,158).

[0033] The placement of the embolism collection element (e.g., vacuum)is important only to the extent that it enhance the ability of theoverall assembly to collect fragmented portions of the clot. AlthoughFIG. 1 shows the collector element as extending to the distal end ofassembly, such is not required. If the collector element proves to betoo thick and causes the more distal portion of the element to becomeinflexible or ungainly, the most distal portion of the element may beomitted. Although the collection element is shown in the FIGs asbuilt-into to the occlusion-removing device, it is to be understood thatit can be external to the device and, furthermore, that the collectionelement could be inserted after the device has been used to shear atleast a portion of the occlusion. Vacuum aspirators used in surgicalprocedures and other suitable collection elements are well known and, inview of the present specification, one of skill in the art could readilyinclude such elements in the devices described herein.

[0034] In certain embodiments, the device includes a drive shaft (13)disposed within the housing. Any suitable drive shaft designs can beemployed, for example, as described in U.S. Pat. No. 5,423,838. As shownin FIG. 1, the drive shaft occupies the inner lumen of the housing ofthe assembly. Furthermore, the distal end portion of the shaft (13) isattached to the cutting element. Attachment of the cutting element tothe drive shaft may be by any convenient procedure, e.g., soldering,welding, gluing, etc. In embodiments in which the device will carryfluids, the drive shaft is preferably sealed from the rest of thecomponents. Furthermore, as with the housing, the drive shaft can bemodified (e.g., by braiding and/or roughening) to enhance shearing ofthe occlusion within the device.

[0035] The operation of the device (e.g., balloon, vacuum and/or cuttingelement) is preferably controlled by the operator via one or moreactuators. For example, the inflatable balloon element is collapsiblefor passage to the embolism and is expanded as desired at the selectedlocation by the operator. Similarly, the operator can use an actuator tomanipulate the cutting element, e.g., using the drive shaft, to shearthe occlusion. The embolism collection element and/or fluid channel alsopreferably are controllable by the operator. As noted above, eachelement may be operated by a different actuator or, in some embodiments,the same actuator may control more than one element. Furthermore, theactuator may be independently produced from the embolectomy device ormay be produced integrally with it. Other procedures and devices may,obviously, be used to expand the balloon.

[0036] Thus, one or more functions of the device (e.g., shearing of theocclusion; aspiration, fluid collection and release, etc.) can beachieved using energy supplied by the operator, for instance using anactuator (or actuators) operably linked to the elements of the devicethat require manipulation. Alternatively, the energy required for one ormore of the functions of the device are supplied from a power source,for example, a motor operably linked to the drive shaft or a motor whichdrives rotation of the cutting element. Power source may supplyelectrical power, for example alternating current, direct current oralternating current superimposed over the direct current signal.Including links and transmission capability through the catheter and/ordevice is well within the purview of the skilled artisan, as describedfor example, in co-owned U.S. Pat. No. 6,168,592. Accordingly, one ormore elements of the device may be operably connected to a power source,such as through a power transmission device embedded in, or external to,the device.

[0037] In certain embodiments, one or more functions of the device(e.g., rotation of the cutting element) are controlled by amicro-electro-mechanical system (MEMS) or micromotor. An MEMS is adevice that transforms mechanical activity into electrical signals andvice versa. (see, e.g., U.S. Pat. Nos 6,201,980; 6,060,336 and documentscited therein) and have been used in a variety of applications,including as micromotors. In the context of the present invention,therefore, MEMS motors (also known as actuators) can be used to control,for example, rotation of the cutting element. The MEMS motor can bedirectly fabricated into the device (for example, on one or more waferson the tip of the catheter) with other required circuit components, toform an integrated, MEMS-driven device. Alternatively, the MEMS can beexternal to the device, yet connected so as to provide the necessarypower. In any event, when used with MEMS-type actuators, the assemblieswill further include any fluid channels and/or other transmissiondevices necessary for MEMS function. Furthermore, including an MEMSmicromotor can, in some instances, eliminate the need for, or reduce thelength of, the drive shaft. Methods of manufacturing and using suitableMEMS are know to those of skill in the art and include, by way ofexample, bulk micromachining; surface micromachining; wafer bonding; andLIGA and Electroforming.

[0038] The occlusion-removal assembly may also include radio-opaquematerial, for example as part of the housing, cutting element, orcasing. Additionally, radio-opaque bands may be included at the distaltip of the assembly for the purpose of allowing the user to visualizethe tip of the assembly in relation to the embolism to be removed. Thus,one or more of the elements (e.g,. housing, cutting element, etc.) ofthe device preferably includes at least one region that is radio-opaqueto facilitate visualization in situ.

[0039] The device may be deployed using a guide wire, for example theindividual components designed to be deployed over a guide wire. Inthese embodiments, a channel to accommodate the guide wire will beincluded in one or more of the following elements: housing, cuttingelement, collection element and balloon.

[0040] In certain embodiments, rapid exchange type catheters are used todeploy any of the devices described herein. Rapid exchange catheters arewell known to those of skill in the art and are described, for example,in U.S. Pat. Nos. 5,919,164 and 5,827,229. Briefly, rapid exchangetypically involves a short guide wire inserted into a slit in thecatheter near the proximal end. Partial rapid exchange design can beaccomplished using a long guidewire lumen with a slit from the proximalend, extending to several inches (less than 10 cm) from the distal end.The operator can load the device into the catheter over the short rapidexchange length guidewire and insert the assembly into to the coronaryarteries.

[0041] The device is obviously dimensioned such that is can fit in theselected pathways. For neurovascular indications, the housing may bebetween 0.1 to 10 mm in diameter; the cutting element between 0.8 and0.9 mm and the inflated balloon between 1 and 30 mm in diameter. Forperipheral vasculature, the dimensions will typically be larger. It willbe apparent that such dimensions are not critical to the practice of theinvention and be readily determined by the skilled artisan in view ofthe teachings herein.

[0042] Modifications of the procedure and device described above, andthe methods of using them in keeping with this invention will beapparent to those having skill in this mechanical and surgical art.These variations are intended to be within the scope of the claims thatfollow.

What is claimed is:
 1. A device for removing occlusions from a vessel,comprising a housing element having a distal end, a proximal end and alongitudinal axis, wherein one or more lumens are disposed along thelongitudinal axis; an embolism collector element; a cutting elementattached to the distal end of the drive shaft; and an inflatableballoon.
 2. The device of claim 1, further comprising a fluid channel inoperable communication with the cutting element.
 3. The device of claim1 or 2, further comprising a casing disposed around cutting element. 4.The device of claim 1, further comprising a drive shaft disposed alongthe longitudinal axis of the housing.
 5. The device of claim 1, furthercomprising a power source connected to the cutting element.
 6. Thedevice of claim 5, wherein the power source comprises a micro electromechanical system (MEMS) motor.
 7. The device of claim 1, wherein theembolism collector element is disposed along the longitudinal axis ofthe housing.
 8. The device of claim 7, wherein the collector elementcomprises a vacuum aspirator.
 9. The device of claim 1, wherein thesurface of the cutting element is not smooth.
 10. The device of claim 1,wherein the cutting element further comprises perforations therein. 11.The device of claim 1, wherein the lumen of the housing which contactsthe cutting element is surface-modified.
 12. The device of claim 3,wherein the surface of the casing surrounding the cutting element issurface-modified.
 13. The device of claim 11 or claim 12, wherein thesurface modification comprises braiding or ribbons.
 14. The device ofclaim 3, wherein the casing extends from the distal end of the housing.15. The device of claim 3, wherein the casing comprises a cage-likestructure.
 16. The device of claim 1, wherein the inflatable balloon iscapable of centering the cutting element.
 17. The device of claim 1,wherein the inflatable balloon is capable of at least partiallyarresting blood flow around the occlusion.
 18. A method of removing anocclusion in a vessel, comprising accessing a selected site with thedevice according to claim 1; inflating the balloon to the desireddimensions; shearing at least a portion of the embolism with the cuttingelement; and removing the sheared fragments of the embolism with thecollection element.
 19. The method of claim 18, wherein the shearingcomprises: drawing a portion of the embolism into the housing andmanipulating the cutting element to shear the embolism against theinterior wall of the housing.
 20. The method of claim 18, wherein thedevice further comprises a casing disposed around the cutting element.21. The method of claim 20, wherein the shearing comprises extending thecutting element and surrounding casing from the distal end of thehousing and manipulating the cutting element against the casing.